I agree with JDJones.. Malecon towards the fort.
Also a nearby place, Plaza de los Bomberos, attract quite a few.
It?s a park with no cars ( only around.. ), people buy a beer or soda in the nearby colmado, just hang out and talk... Nothing special, just relaxing.
Close to the postoffice in POP you have outdoor restaurant Eskina, where you can have great food and a cold one in an outdoor athmosphere...
Mixed public, no tourists. It is a wellkept secret for many of expats and Dominicans..lol..
Youngsters don?t go out and eat here though much..to expensive for locals..
Same street as Eskina, further down towards the port, you?ll find a few poolbars where you will meet young people though..